Preventing Platelet-Derived Microparticle Formation—and Possible Side Effects—With Prestorage Leukofiltration of Whole Blood

Context.—Platelet-derived microparticles (PDMPs) probably function in hemostasis, thrombosis, inflammation, and transfusion-related immunomodulation. Objective.—To compare PDMP levels of leukocyte-filtered and unfiltered whole blood during storage. Design.—Ten whole blood donations were collected and processed. Half of each collection was filtered, half remained unfiltered, and both halves were measured for red cell, white cell, and platelet (PLT) content before storage. Samples were drawn on days 0, 1, 2, 3, 5, 7, 14, 21, 28, and 35 and analyzed by flow cytometry. Results.—Leukocyte filtration lowered prestorage PDMP and PLT counts by an average of 72% and 99%, respectively. Prestorage PDMP counts were 123 ± 51/µL in unfiltered whole blood supernatant versus 34 ± 18/µL after filtration. Prestorage PLT counts were 190 ± 49/µL in unfiltered whole blood supernatant versus 2 ± 4/µL after filtration. Moreover, PDMP and PLT counts in filtered whole blood remained low throughout storage, typically below 100/µL. In contrast, unfiltered whole blood PDMP- and PLT-gated events increased approximately 2 log during storage, with the peak number of PLT-gated events tending to coincide with the peak number of PDMP-gated events (4 donors) or to come after the peak number of PDMP-gated events (6 donors). Conclusions.—Leukocyte filtration of whole blood lowers prestorage PDMP and PLT counts. Platelet-derived microparticle and PLT counts remain low throughout 35 days of storage. In contrast, PDMP- and PLT-gated events increase significantly in unfiltered whole blood. The nature of PLT-gated events in stored blood warrants further investigation.